Low permeability, high strength timing fabric for utilization within airbag inflation modules

ABSTRACT

Specific fabric articles exhibiting very low air and/or gas permeability (even upon application of high inflation pressures) and very high tear strengths are herein disclosed and claimed. Such a specific fabric also permits the incorporation of discrete openings (through cutting, for example) through which air and/or gas introduced by an airbag inflation canister will travel. Such a specific fabric acts as a barrier to the complete introduction of high pressure inflation gases into an airbag cushion, thereby permitting a more controlled, safer inflation upon the occurrence of a collision event. Thus, the specific inventive fabric permits movement of inflation gas and/or air substantially solely through the openings within the fabric and not through the interstices between the individual fiber constituents. The inventive fabric also withstands the intense heat generated by the explosion which creates the inflation gases and does not lose any appreciable degree of performance during and after such an inflation event. An inflation module, as well as an entire vehicle restraint system, comprising such a specific timing fabric is also contemplated within this invention.

FIELD OF THE INVENTION

This invention relates generally to specific fabric articles exhibitingvery low air and/or gas permeability (even upon application of highinflation pressures) and very high tear strengths. Such a specificfabric also permits the incorporation of discrete openings (throughcutting, for example) through which air and/or gas introduced by anairbag inflation canister will travel. Such a specific fabric acts as abarrier to the complete introduction of high pressure inflation gasesinto an airbag cushion, thereby permitting a more controlled, saferinflation upon the occurrence of a collision event. Thus, the specificinventive fabric permits movement of inflation gas and/or airsubstantially solely through the incorporated openings within the fabricand not through the interstices between the individual fiberconstituents. The inventive fabric also withstands the intense heatgenerated by the explosion that creates the inflation gases and does notlose any appreciable degree of performance during and after such aninflation event. An inflation module, as well as an entire vehiclerestraint system, comprising such a specific timing fabric are alsocontemplated within this invention.

BACKGROUND OF THE PRIOR ART

All U.S. patents cited herein are hereby fully incorporated byreference.

Inflatable protective cushions used in passenger vehicles are acomponent of relatively complex passive restraint systems. The mainelements of these systems are: an impact sensing system, an ignitionsystem, a propellant material, an attachment device, a system enclosure,and an inflatable protective cushion. Upon sensing an impact, thepropellant is ignited causing an explosive release of gases filing thecushion to a deployed state which can absorb the impact of the forwardmovement of a body and dissipate its energy by means of rapid venting ofthe gas. The entire sequence of events occurs within about 30milliseconds. In the undeployed state, the cushion is stored in or nearthe steering column, the dashboard, in a door, in the roof line or roofrail, or in the back of a front seat placing the cushion in closeproximity to the person or object it is to protect.

Inflatable cushion systems commonly referred to as air bag systems havebeen used in the past to protect both the operator of the vehicle andpassengers. Systems for the protection of the vehicle operator havetypically been mounted in the steering column of the vehicle and haveutilized cushion constructions directly deployable towards the driver.These driver-side cushions are typically of a relatively simpleconfiguration in that they function over a fairly small well-definedarea between the driver and the steering column. One such configurationis disclosed in U.S. Pat. No. 5,533,755 to Nelsen et al., issued Jul. 9,1996, the teachings of which are incorporated herein by reference.

Inflatable cushions for use in the protection of passengers againstfrontal or side impacts must generally have a more complex configurationsince the position of a vehicle passenger may not be well defined andgreater distance may exist between the passenger and the surface of thevehicle against which that passenger might be thrown in the event of acollision. Prior cushions for use in such environments are disclosed inU.S. Pat. No. 5,520,416 to Bishop; U.S. Pat. No. 5,454,594 to Krickl;U.S. Pat. No. 5,423,273 to Hawthorn et al.; U.S. Pat. No. 5,316,337 toYamaji et al.; U.S. Pat. No. 5,310,216 to Wehner et al.; U.S. Pat. No.5,090,729 to Watanabe; U.S. Pat. No. 5,087,071 to Wallner et al.; U.S.Pat. No. 4,944,529 to Backhaus; and U.S. Pat. No. 3,792,873 to Buchneret al.

The majority of commercially used restraint cushions are formed of wovenfabric materials utilizing multifilament synthetic yarns of materialssuch as polyester, nylon 6 or nylon 6,6 polymers. Representative fabricsfor such use are disclosed in U.S. Pat. No. 4,921,735 to Bloch; U.S.Pat. No. 5,093,163 to Krummheuer et al.; U.S. Pat. No. 5,110,666 toMenzel et al.; U.S. Pat. No. 5,236,775 to Swoboda et al.; U.S. Pat. No.5,277,230 to Sollars, Jr.; U.S. Pat. No. 5,356,680 to Krummheuer et al.;U.S. Pat. No. 5,477,890 to Krummheuer et al.; U.S. Pat. No. 5,508,073 toKrummheuer et al.; U.S. Pat. No. 5,503,197 to Bower et al.; and U.S.Pat. No. 5,704,402 to Bowen et al. A two-weave construction airbagcushion is exemplified in U.S. Pat. No. 5,651,395 to Graham et al. butdoes not discuss the importance of narrow basket-weave single fabriclayers.

As will be appreciated, the permeability of an airbag cushion structureis an important factor in determining the rate of inflation andsubsequent rapid deflation following the impact event. Different airbagcushions are utilized for different purposes. For instance, some airbagcushions are installed within inflation modules for driver protectionwithin the steering column of an automobile. Others are utilized asprotection for front seat passengers and are installed in and around theglove compartment and/or on the dashboard in front of such a passengerseat. Still others have been developed in an effort to protect allpassengers during a long-duration impact event, such as, for example, arollover collision. In those types of crashes, the target airbag cushionmust inflate quickly under high pressure (such as between about 10 and40 psi) and remain inflated at a relatively high pressures in order toprovide the greatest degree of protection to such passengers.Furthermore, such long-duration airbag cushions preferably comprise“pillow” formations created through the attachment of at least twodifferent fabrics or fabric ends together and sealed, sewn, or the like,together. Upon inflation the free space between the attachment pointsinflate as well, thereby producing the desired cushioned “pillow”structures. Such long-duration, “pillowed” structures have beendisclosed in the prior art as airbag cushions within U.S. Pat. No.5,788,270 to Halano as well as within U.S. patent application Ser. No.09/406,264 to Sollars, Jr., now U.S. Pat. No. 6,220,309.

Generally, recent airbag improvements have involved various types ofalterations to either the bag structures and/or coatings, or, mostimportantly for this invention, the inflators and propellants utilizedto provide more effective and safer supplemental vehicle restraintsystems. In the past, the standard inflators produced extremely hot andpotentially destructive explosions during propellant ignition toeffectively and quickly (e.g., in less than 0.2 milliseconds) introducesufficient amounts of inflation gas into the desired airbag to protect apassenger or driver during a collision. In recent years, more controlledand safer inflation modules have been developed which still providehighly effective inflations as needed. However, some drawbacks haveresulted, particularly within and for larger airbag which requirelong-term, sustained inflation (such as side curtain-type airbags). Mostnotably, such airbags must be inflated at an even rate to provide themost efficient and effective protection to the vehicle occupants. The“pillowed” structures within the target side curtain airbags thus need arelatively similar inflation pattern. Since most inflators for suchairbags have been developed to inflate from a single small area andforce inflation gas to portions of the target airbags at differingdistances from the point of ignition, controlled inflation at similarspeeds have been extremely difficult. New developments, such as thatdisclosed within European Patent Application 0,995,645 A2 to OEA, Inc.have provided highly desirable procedures and apparati to inflate suchside curtain airbags in more efficient and effective manners. In thisspecific Application, the ignited propellant is forced into an inflationmanifold (for example, a rubber tube) located in the roofline of thevehicle. This manifold comprises openings at selected locations whichpermit passage of certain limited amounts of inflation gas to eventuallyenter and inflate the target airbag, particularly within the specific“pillowed” structures, on an even basis. However, even with this systemin place, there still exists a need to control the limited amounts ofinflation gas in order to assure a controlled and effective airbaginflation. Thus, there is also taught the addition and use of a timingmember, such as a plastic or metal, which itself comprises openingscorresponding to those present within the inflation manifold. This metalor plastic timing member is preferably present in a tube shape as welland will inflate to a very low degree, if at all, upon entry of theinflation gas from the inflation manifold. However, inflation gas willalso be forced through the openings within the timing member and theninto the airbag for inflation. Although the actual time of inflation isincredibly fast (again, no more than about 0.2 milliseconds), theability to provide controlled and even inflation, as well as to betterensure the airbag does not overinflate or inflate too quickly isparamount to providing a safe and effective supplemental vehiclerestraint system of this type. Without such a timing member, thecontrolled inflation would be extremely difficult if not impossible dueto the incredible, yet necessary, force produced upon ignition of thepropellants in order to actually provide the quick inflation of thetarget airbag.

Furthermore, with regard to this OEA, Inc. European Patent Application,high temperature inflation gases are generated during the propellantignition, both as a result of such an explosion and in order to assurefull inflation of the target airbag. If the inflation is too cool intemperature, the gases will not expand sufficiently and thus the targetairbag will not fully inflate. Thus, it is, as noted above, extremelyimportant to permit sufficient, though not too much, inflation gases topass through the openings within the metal or plastic timing member. Thepassage of too much inflation gas (through, for example, weak or damagedareas within the timing member) would actually cool the inflation gasand prevent the desired degree of airbag inflation. However, there isalso a problem with such excessive generated heat in that the targetairbag may conduct such heat to the vehicle occupant. Such problems maybe alleviated by the application of exterior and/or interior coatings tothe target airbag; however, the presence and utilization of the metal orplastic timing member aids in this instance as well.

Although such a timing member has been taught in the past as a desiredcomponent within such new airbag inflation systems, there have noteachings concerning fabrics utilized as timing members with any suchhigh pressure inflation assemblies. Fabrics are most highly desired forsuch a purpose due to costs, ease of manufacture, foldability,unfoldability (upon inflation), lower weight, and many other reasons.Such a practice of fabric timing members has been limited, if notimpossible, due to the difficulties in developing a proper fabric forthis specific purpose. Again, the fabric must be able to withstandextremely high pressures and tensile forces during inflation, excessiveheat during inflation, and must effectively permit the vast majority ofinflation gas to escape through the provided openings which correspondto the inflation manifold openings, and thus must exhibit extremely lowair and gas permeabilities in the remaining portions of its constituentfabric. Furthermore, since such a timing member will be folded duringstorage for an indefinite amount of time prior to use, it must alsoexhibit extremely good blocking characteristics such that the fabricportions do not adhere together in a deleterious manner such that uponinflation the timing member does not unfold properly and thus does notfunction as needed. There have been no teachings or developments of suchfabric timing member meetings all of these objectives to date within thepertinent prior art. Thus, there is a perceived need to provide such aneffective fabric timing member in order to make available to the airbagindustry these new, safe, and highly effective inflation modules.

In light of the background above, it can be readily seen that thereexists a need for an effective fabric timing member for utilizationwithin such specific airbag inflation assemblies having inflationmanifolds for the transport of inflation gas from the propellantignition location ultimately into the target airbag article. The reasonsfor utilizing a fabric for such a timing member include, withoutlimitation, the ability to expand and unfold (and thus the ability tofold and pack well within the inflation assembly itself) upon inflation,the low costs involved with producing fabrics as opposed to otherinflation articles (including metal articles), lighter weight inflationassemblies, reduction of complex parts within the inflation assembly,simplification of inflator design and function, and adaptability of suchan inflation assembly to multiple inflation applications. Furthermore,in furtherance of these objectives, such a fabric permits the ability toprovide strength to specific areas of the timing member through weaveformations or insertions of extra threads, and the ability to control(preferably lower and eliminate, if possible) the air permeability ofthe timing member through the application of coating compositions to thesurfaces thereof. Thus, although alternative articles and structures mayprovide some of the characteristics necessary for proper functioningwithin an inflation assembly as described above, in short, theutilization of fabrics for this purpose is most highly desired.

Such fabric utilization within an inflation assembly timing member hasbeen rather difficult to achieve until now, unfortunately. It is truethat fabrics have been utilized as the primary constituents withinairbags themselves (which must withstand heat and high inflationpressures); however, such fabrics have not proven useful and/or workableas timing members. Traditional airbag fabrics are structured to eitherpermit quick inflation and then quick deflation (such as within driverand front-seat passenger side airbags, and also certain non-rolloverprotection side curtains) or long-term inflation (to protect in rolloversituations, such as the side curtain-type airbags discussed above). Assuch, the fabrics utilized are not conducive to actually acting in acontrolling fashion for extremely high pressure and high temperatureinflation gases. The tensile strengths exhibited by these traditionalairbag fabrics do not exceed 400 pounds per square inch (or about 675newtons per centimeter). The timing member must exhibit a far greatertensile strength on the order of at least about 900 lb/inch in the warpdirection (preferably between about 950 and 1,500 lb/inch, morepreferably between about 1,000 and 1,250 lb/inch, and most preferablyfrom about 1,000 to about 1,100 lb/inch) and at least 700 lb/inch in thefill direction (preferably between about 750 and 1,200 lb/inch, morepreferably between about 800 and 1,000 lb/inch, and most preferablybetween about 800 and 900 lb/inch). Furthermore, the high temperatureswithstood by the traditional airbag fabrics are generally much lowerthan those required of such a timing member (due to the location of theentire timing member in relation to the actual point of propellantignition as compared with an airbag cushion). Thus, it is evident thatalthough airbag fabrics have been developed in the past to withstandcertain high inflation pressures and temperatures, such fabrics do notfunction properly as timing members within the new inflation assemblies(as discussed above) due to the pressures and temperatures which exceedsuch limits.

Other fabrics have been developed as filter fabrics for airbags, such asin U.S. Pat. No. 5,441,798 to Nishimura et al., which permit control ofinflation to prevent too rapid and excessive airbag expansion uponignition of a propellant. However, such filter cloths and fabrics do notinclude specific openings through which substantially all of theinflation gasses are transported into the target airbag. In fact, thefabrics discussed and disclosed by patentee actually exhibit relativelyhigh air and/or gas permeabilities as opposed to the required lowpermeabilities exhibited by the inventive timing member. Due to suchhigh permeability characteristics, the tensile strength of the patentedfilter cloth within Nishimura et al. is apparently relatively low (onthe magnitude of standard airbag fabrics themselves) which thus, again,would prevent utilization of such a patented filter cloth as a timingmember within the inflation assemblies discussed above.

OBJECTS AND DESCRIPTION OF THE INVENTION

As such, it is an object of this invention to provide a fabric forproper functioning as a timing member for a high pressure inflationassembly comprising an extended inflation gas manifold. A furtherobjective is to provide a relatively inexpensive high tensile strength,low air and/or gas permeability timing fabric for controlled inflationof an airbag cushion.

Accordingly, this invention is directed to an airbag inflation assemblytiming member comprising discrete openings in relation to preselectedlocations for introduction of inflation gas within a target airbag;

wherein said timing member comprises a fabric;

wherein a coating has been applied to at least a portion of said fabric;and

wherein said timing member exhibits (a) an average overall tensilestrength of at least 900 lb/inch in the warp direction and an averageoverall tensile strength of at 700 lb/inch, both up to a temperature ofat least 80° C., (b) a permeability to air of at most 0.07 cfm at 125 Paand of at most 0.3 cfm at 2,500 Pa, and (c) no appreciable blocking uponinflation upon storage in an environment heated to about 100° C. for 7days.

As noted above, the term timing member is intended to encompass anarticle of manufacture which acts to control the movement, in bothdirection and amount, of inflation gasses from an inflator (generallycomprising a propellant and a means to ignite said propellant uponsensing a collision of sufficient impact to require the need for asupplemental vehicle restraint system for then vehicle occupants). Thisarticle is described more fully within the drawings as described below.Such an inventive timing member permits movement of inflation gassessubstantially solely through the preselected location openings in orderto ensure the inflation gasses are directed into desired and discretelocations within the target airbag. This fabric article thus mustexhibit the aforementioned tensile strength and low permeabilitycharacteristics in order to ensure the inflation gases are in factforced solely through the preselected openings and do not leak throughthe interstitial spaces between constituent fibers. Additionally, thetensile strength requirements best ensure that the timing member willnot exhibit tears as a result of forcing an excessive amount ofinflation gas through the small preselected openings. As one of ordinaryskill in the art will appreciate, the pressure applied to such anopening would most likely create a larger opening depending on theweakness of the fabric present in the areas surrounding the openingsthemselves. In this situation, the timing member fabric is of sufficienttensile strength to prevent such deleterious tearing, thereby providingan effective means to control the amount and direction of inflation gasinto the target airbag. The fabric of the timing member may be woven,laid scrim, or knit in structure. Preferably, such a fabric is woven inany number of weave formations, including plain weave, panama weave,dobby weave, and the like, and may be produced on any type of weavingloom including, without limitation, shuttle, rapier, air-jet, andwater-jet looms. Preferably, the timing member fabric is of plain weaveconstruction produced on a rapier loom (due to the utilization of highdenier yarns). Furthermore, the picks by ends (per square inch offabric) count of such a fabric ranges anywhere from about 40 by 40 toabout 60 by 15. Preferably, such a count is from about 45 by 35 to about55 by 20, more preferably from about 50 by 30 to about 54 by 20, andmost preferably about 54 by 22.

Of critical importance to achieve this desired level of tensile strengthand thus the ability to control inflation gas from the inflationassembly into the target airbag are the elongation characteristicsexhibited by the overall timing member. In particular, it has been foundthat the utilization of a low-shrink, high elongation warp yarn and alow elongation fill yarn provides the necessary high tensile strengthlevels. In this manner, the warp yarns permit expansion of the timingmember upon sudden inflation to compensate for the quick increase inpressure applied to the fabric article but the fibers do not allelongate, thereby limiting the expansion, and, in particular, preventingappreciable amounts of air from escaping between the very thick warpyarns and the low elongation fill yarns. The warp elongation absorbs theinitial shock to the fabric due to the quick and high pressure inflationwhile the fill yarns permit retention of shape, location, andultimately, direction of movement of the timing member in relation tothe inflation itself. The fill yarns are thus of extremely high denier(at least 840, preferably in excess of 1000, and most preferably as highas about 1600) and may be single or multi-ply as well. The warp yarnspreferably, though not necessarily, are comprised of a two-ply, highdenier fiber, such as, without limitation polyester (polyethyleneterephthalate), nylon, and the like, preferably polyester. The deniermust be 840 or higher to fill the interstitial spaces for permeabilityreduction. Preferably, this warp yarn is a two-ply yarn of individualfibers of 840 denier (average) each or higher. Multi-ply yarns ofgreater than 2-ply may also be utilized as well as single ply yarns thatexhibit proper elongation and bulkiness (i.e., sufficient denier to fillthe interstitial spaces). Again, however, 2-ply 840 denier polyesteryarns are most preferred due to cost, strength, and availability.

The low permeability level necessary for proper functioning by thetiming member for its intended purpose is provided through thecombination of the high denier yarns within the fabric structure as wellas the presence of a seal coating over at least a portion of the fabricconstituents within the timing member. As is well known throughout theairbag industry and art, coatings have been applied to airbag cushionsand fabrics to provide low permeability characteristics to the coatedairbag fabric portions. In this instance, the low permeabilitycharacteristics are provided in much the same manner as with standardairbags except that the pressures applied to the discrete areassurrounding the preselected openings within the timing member aresubject to much greater stresses and forces than inflated airbags.Again, the presence of bulkier yarns (standard airbag fabrics compriseat most 840 denier yarns, which is still a rare occurrence; generally,420 to 630 denier is used for such standard fabrics) provides a moreeffective barrier to gas escape through the interstitial portionsbetween the fibers and also provides the need for coatings of relativelylow thicknesses to be applied thereto. Such coatings may comprisestandard silicones (polyorganosiloxanes, for example), polyurethanes,polyarnides, rubbers, such as neoprene, ethylene-propylene diene monomerrubber (EPDM), hydrogenated nitrile-butadiene rubber (NBR), butylrubber, acrylic rubber, and the like, in add-on weights of between about0.8 ounces per square yard and 6.0 ounces per square yard. The lower thecoating add-on weight the better due to the costs of such materials. Thecoating is applied to the target fabric surface through any well knownmeans such as knife coating, scrape coating, immersion coating, spraycoating, pad coating, and the like. Preferably, such a coating isapplied through a standard knife over gap procedure in order to apply arelatively uniform coating over the individual yarns as well as withinthe interstitial spaces between the yarns themselves. Other possiblecomponents present within the cross-linked elastomeric resin coatingcomposition are thickeners, antioxidants, flame retardants, coalescentagents, adhesion promoters, and colorants.

The coating is utilized not just for the reduction of gas permeabilitybut also to provide a manner of preventing heat conduction from theinflation assembly ultimately to the vehicle occupant. Thus, suchcoatings help absorb a great deal of heat in such an instance while theremaining, potentially harmful high temperatures are absorbed by thecoatings and fabrics of the actual target airbag cushion. It isimportant to remember, and thus note, that the temperature of theinflation gas is not reduced by the coatings applied to the timingmember fabric since a sufficiently high temperature is required toactually inflate the target airbag in the first place. The coatingsimply absorbs excess heat and acts as a buffer to conduction of suchheat to the exterior of the target airbag upon inflation.

In addition, it is also important that the timing member withstand notonly heat but also cold temperatures, particularly during long-termstorage within an automobile. Again, the potential occurrence of acollision is impossible to determine; thus, the inflation assembly andits constituent parts must function properly at any time during thelifetime of the vehicle itself. Thus, with the potential for coldtemperatures during such a lifetime, the fabric of the timing membermust not be deleteriously affected by such diverse temperatures. Thecoating provides some reassurance in such a situation by protecting thefibers from the effects of cold temperatures.

The thinner the coating the better the blocking characteristics for thefabric. This property is of utmost importance to best ensure the foldedtiming member will not adhere together to such an extent that uponinflation the fabric portions do not permit the correct directionalcontrol of inflation gas. Thus, a thickness of relative uniformity offrom about 1.0 to about 2.0 ounces per square yard of fabric, morepreferably from about 1.2 to about 1.8 ounces per square yard, and mostpreferably from about 1.4 to about 1.6 ounces per square yard isdesired. The timing member fabric must thus pass a blocking test whichindicates the force required to separate two portions of coated fabricfrom one another after prolonged storage in contact with each other(such as an airbag is stored). Laboratory analysis for blocking entailspressing together coated sides of two 2 inch by 2 inch swatches ofairbag fabric at 5 psi at 120° C. for 7 days. If the force required topull the two swatches apart after this time is greater than 50 grams persquare yard, or the time required to separate the fabrics utilizing a 50gram weight suspended from the bottom fabric layer is greater than 10seconds, the coating fails the blocking test. Clearly, the lower therequired separating shear force, the more favorable the coating.

Of particular importance and of unexpected benefit is the ability tocoat the timing member fabric components without first cleaning orscouring such to remove certain finishing agents, yarn lubricants, andthe like. The timing member should comprise yarns which are twisted andplied to a degree wherein size is generally unnecessary (although, inother embodiments, size may be applied prior to weaving, knitting, etc.)to permit reliable construction (through weaving, knitting, etc.).Generally, in order to apply reliable air permeability reducing amountsof coating materials (in this invention, a coating of sufficientconstruction and thickness to reduce the permeability to at most 0.3cfm), the fabric must first be cleaned and/or scoured to remove thepotentially deleterious adhesion-reducing size and/or lubricants. Inthis invention, it has now been realized that the bulkiness of theconstituent yarns and fibers, and the lack of size for proper fabricconstruction, permits effective adhesion with or without the presence ofsuch lubricant materials and/or finishing agents thereon. As such, it isbelieved that the inventive timing member is the first such fabricmaterial to exhibit such low air permeability through the presence of acoating applied thereto, but which also is an unscoured and/or uncleanedfabric prior to application of such coating, but after constructionthereof.

Another test which the specific coated timing member fabric must pass isthe oven aging test. Such a test also simulates the storage of a fabricover a long period of time upon exposure at high temperatures andactually is used to analyze alterations of various different fabricproperties after such a prolonged storage in a hot ventilated oven(>100° C.) for 2 or more weeks. For the purposes of this invention, thistest was used basically to analyze the air permeability and tensilestrengths of the coated timing member fabric after storage under apressure of about 125 Pascals. Such coated timing member fabricsgenerally should exhibit an air permeability level of less than about0.2 cfm at 125 Pa. Again, the lower the air permeability, the better thecoating.

While the invention will be described and disclosed in connection withcertain preferred embodiments and practices, it is in no way intended tolimit the invention to those specific embodiments, rather it is intendedto cover equivalent structures structural equivalents and allalternative embodiments and modifications as may be defined by the scopeof the appended claims and equivalence thereto.

PREFERRED EMBODIMENTS OF THE INVENTION

In accordance with the potentially preferred practices of the presentinvention, a solvent-borne (e.g., toluene) microdispersion of finelydivided elastomeric resin (such as self-cross-linking silicone, e.g.,polyorganosiloxane particles) is compounded with a thickener and a flameretardant to yield a compounded mix having a viscosity of about 8000centipoise or greater. The potentially preferred silicone dispersion ismarketed under the trade designation 4-7224 Silicone Rubber from DowCorning. Other preferred cross-linked elastomeric resins includepolyurethane, such as WITCOBOND™ 253 (35% solids), from Witco, andSANCURE®, from BFGoodrich, Cleveland, Ohio; hydrogenated NBR, such asCHEMISAT™ LCH-7335X (40% solids), from Goodyear Chemical, Akron, Ohio;EPDM, such as EP-603A rubber latex, from Lord Corporation, Erie, Pa.;butyl rubber, such as Butyl rubber latex BL-100, from Lord Corporation;acrylic rubber (elastomers), such as HYCAR™, from BFGoodrich; polyarmidedispersions, such as MICROMID® hpl, from Union Camp; thermoplasticpolypropylene, such as P947M-026 from Huntsman Petrochemical; andpossibly polyethylene terephthalate, such as RITEFLEX® from Ticona. Apotentially preferred thickener is marketed under the trade designationNATROSOL™ 250 HHXR by the Aqualon division of Hercules Corporation whichis believed to have a place of business at Wilmington, Del. Thecross-linking agent may be any such compound which is well known in theart, such as melamine formaldehyde, and the like.

In order to meet Federal Motor Vehicle Safety Standard 302 flameretardant requirements for the automotive industry, a flame retardant isalso preferably added to the compounded mix. One potentially preferredflame retardant is AMSPERSE® F/R 51 marketed by Amspec ChemicalCorporation which is believed to have a place of business at GloucesterCity N.J.

Once compounding is complete, the formulation is preferablyscrape-coated across the fabric substrate and dried and cured to form athin coating. Scrape coating in this sense includes, and is not limitedto, knife coating, in particular knife-over-gap table, floating knife,and knife-over-foam pad methods, to name a few different method types.Such scrape coating permits most of the coating resin to remain withinthe interstices of the yarns of the airbag fabric. It is within theseinterstices that air is most likely to leak from an inflated airbagwithout any coating present. Furthermore, scrape coating permits verylittle resin to be applied to the raised yarn of the airbag fabric atthis low coating weight. As a result, this particular distribution ofcoating materials on the surface of the airbag fabric allows thecross-linked elastomeric resin coating to seal the fabric while the lowcoating weight also simultaneously restricts contact between resinsamples located on different portions of the fabric surface. Thischaracteristic is very important to ensure the subject fabric will passthe required blocking test, described above.

The final dry weight of the coating is preferably about 2.0 ounces persquare yard or less and most preferably 1.0 to about 1.5 ounces persquare yard. The resultant base fabric is substantially impermeable toair when measured according to ASTM Test D737, “Air Permeability ofTextile Fabrics,” standards.

In order to further describe the present invention the followingnonlimiting examples are set forth. The polyarnide elastomer discussedabove and described in more detail below is the most preferredembodiment of the invention. These examples are provided for the solepurpose of illustrating some preferred embodiments of the invention andare not to be construed as limiting the scope of the invention in anymanner.

EXAMPLE 1

A fabric was woven on a Dornier rapier loom which comprised, as warpyarns, two-ply and twisted unsized polyethylene terephthalate 840 denierT-787 yarns (from KoSa), and, as fill yarns, single-ply polyethyleneterephthalate 1300 denier T-800 yarns (also from KoSa), in a plain weavepattern at 51 ends by 22 picks per inch of base fabric. The woven fabricexhibited an overall weight of about 17.5 ounces per square yard and athickness (on average) of about 835 microns. The fabric was then,without scouring or cleaning of the fabric, coated with a solvent-basedsilicone coating comprising 30% of 4-7224 Silicone Rubber from DowCorning at a final dry add-on coating weight of 1.5 ounces per squareyard (on average) utilizing an 830 micron gap setting on the knifecoater, which permitting complete filling of the yarn interstices andminimized excess covering of the warp ends (in order to reduceblocking). Talc was applied over the coating as an anti-blocking agentas a supplemental measure to prevent blocking due to cohesion betweendiscrete coated fabric portions. After coating, the fabric was thencured at a temperature of about 170° C. Such a temperature alsopermitted controlled shrinkage of the coated fabric to a finalconstruction of about 54 ends by 22 picks per inch with a resultantfabric weight of about 19.5 ounces per square yard.

This fabric was then sewn into an enclosed tube with specific discreteopenings cut therein to correlate to specific openings present within aninflation module manifold. The fabric exhibited an air permeability ofabout 0.24 cfm through the interstices of the yarns upon application ofair pressure of about 2,500 Pa (as well as an air permeability of about0.02 cfm upon application of air pressure of about 125 Pa). Furthermore,the warp direction tensile strength measured 1,015 lb/in with anelongation of about 43.0% at break and the filling direction tensilestrength measured 836 lb/in with an elongation of about 33% at break.The fabric also passed the aforementioned blocking test easily.

EXAMPLE 2

The same base fabric as in EXAMPLE 1 was produced but coated at a gapsetting of about 950 microns (for thicker coating). The resultantcoating add-on dry weight was about 2.0 ounces per square yard and,after curing at a temperature of about 170° C., the resultant totalweight of the fabric was about 20.0 ounces per square yard. Theresultant air permeability was measured to be 0.12 cfm at 2,500 Pa andthe warp direction tensile strength measured 1,128 lb/in with anelongation of 44.3% at break. The resultant fill direction tensilestrength measured 838 lb/inch with an elongation of 33.3% at break. Thefabric also passed the aforementioned blocking test (although the timerequired for separation was a slower than for the fabric of EXAMPLE 1).Although such an alternative is potentially preferred, this examplerequired a slower line speed to coat the target fabric and the amountapplied was in excess of that needed to provide the low air permeabilitydesired.

EXAMPLE 3

The same base fabric as in EXAMPLE 1 was produced but coated at a gapsetting of about 730 microns (for thinner coating). The resultantcoating add-on dry weight was about 1.4 ounces per square yard and,after curing at a temperature of about 170° C., the resultant totalweight of the fabric was about 19.4 ounces per square yard. Theresultant air permeability was measured to be 0.26 cfm at 2,500 Pa warpdirection tensile strength measured 1,034 lb/in with an elongation of45.3% at break. The resultant fill direction tensile strength measured865 lb/inch with an elongation of 33.7% at break. Thus, even at such alow coating add-on weight, the interstices were completely filled so asto insure adequate control of air permeability and proper blockingmeasurements.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate several potentially preferredembodiments of the invention and together with the description serve toexplain the principles of the invention wherein:

FIG. 1 is a perspective view schematically illustrating the inventiveinflation assembly as incorporated within a non-inflated airbag cushion.

FIGS. 2A-2D are cross-sectional views of the inflation assembly of FIG.1 that schematically illustrate the flow of inflation gas through thetiming member and into the airbag cushion upon activation of thepropellant.

FIG. 3 schematically illustrates one application of the inflationassembly as a side curtain-type airbag inflator with reference to aninterior side view of a vehicle.

FIG. 4 schematically illustrates the inflation assembly of FIG. 3 withreference to a front view of a vehicle.

DETAILED DESCRIPTION OF THE DRAWINGS

Reference will now be made in detail to potentially preferredembodiments of the invention, examples of which have been illustrated inthe accompanying drawings. It is to be understood that it is in no wayintended to limit the invention to such illustrated and describedembodiments. On the contrary, it is intended to cover all alternatives,modifications and equivalents as may be included within the true spiritand scope of the invention as defined by the appended claims andequivalents thereto.

Turning now to the drawings, wherein like elements are denoted by likereference numerals throughout the various views, in FIG. 1 an inflator20 is illustrated including an elongated propellant 28. Upon ignition,the propellant 28 combusts and generates inflation gasses (among othercombustion products) which then inflate the airbag 24. The inflation gasexits through at least one opening 56 within an inflation manifold 52which directs the flow of inflation gas toward the desired airbag 24.Prior to reaching that final destination, the inflation gas first entersand inflates the inventive timing member 96 (preferably constructed asin Example 1, above) which in turn directs the flow of inflation gasthrough at least one of its own preselected openings 100. The propellant28 may be comprised of any well known composition, such as combustiblenitrogen-based formulations (e.g., gun-type propellants comprisinghexahydrotrinitrotriazine and/or cyclotrimethylene trinitramine and/orcyclotetramethylenethanitramine and/or pentaerythritol tetranitrate, andthe like), including binding materials, such as hydroxymethylcellulose,and the like, and other standard propellant components (e.g., ammoniumnitrate, strontium nitrate, colorants, polymeric thickeners, and thelike).

The cross-sectional illustrations of FIGS. 2A-2D exhibit one preferredexample of utilization of the inventive inflation assembly of FIG. 1(and more specifically the inventive fabric timing member 52) uponignition of the propellant 28. In its deactivated state (FIG. 2A), thepropellant 28 has not yet been activated and no inflation gasses havebeen generated. In FIG. 2B, a collision event has occurred that hascaused the initiator assembly 32 to ignite the propellant 28, which inturn generated combustion products, including inflation gas which exitedthe openings 56 within the manifold 52, without rupturing or damagingthe manifold 52 itself. The inflation gasses then enter the chamber 102of the timing member 96 and move radially outward from the outer layer60 of the manifold 52 through the chamber 102 toward the wall of thetiming member 96 and ultimately enter the airbag 24. In FIG. 2C, thereis shown a substantially uniform entry of inflation gasses about thecross-section of the airbag 24, as well as a substantially uniform entryof inflation gases along the entire length of the airbag 24. Suchuniform inflation and filling is provided by means of the predeterminedspacing and sizing of the metering openings 100 within the timing member96. As seen in FIG. 2D, the airbag 24 uniformly receives inflation gasesand is uniformly filled or pressurized throughout its volume by means ofthe timing member 96 by the means noted above. In accordance with thisuniform filling, inflation gases directly from the inflator 20 arefilling the entire airbag 24 rather than inflation gases entering theairbag 24 at a limited area such that, in order to complete filling ofthe airbag 24, inflation gases in the airbag 24 itself are required tomove longitudinally within the airbag 24 in order to achieve the desiredforce or pressure. Such non-uniform filling can result in the vehicleoccupant being subjected to a less than desirable force due to theinflatable filling nonuniformly. With reference to FIGS. 3 and 4, oneapplication of the inflator assembly 20 is schematically illustrated. Insuch an application, the inflator assembly 20 is used with an airbag 24that is located above one or more vehicle side windows. Such an inflatorassembly 20 is commonly termed a side curtain inflator. Such an inflatorassembly 20 is particularly characterized by having a substantiallygreater length, particularly in comparison with driver, passenger, andside impact inflators. As seen in FIGS. 3 and 4, a curtain inflatorassembly 20 is substantially elongated and has a length that is at leastone-half the length of the airbag 24 and preferably is substantiallyequal to the length of the inflator assembly 20. Consequently, when theinflator assembly 20 is activated to deploy or inflate the airbag 24 ofthe curtain inflator module 110, there is a substantially uniformfilling of the airbag 24 along its length. The generation and entry ofinflation gases to the airbag 24 depend on propagation rate associatedwith the combustion wave. That is to say, the filling of the airbag 24along its entire length at substantially the same time is limited by, ordependent upon, the rate at which the elongated propellant 28 is ignitedbeginning at its end adjacent to the initiator assembly 32 andcontinuing to its opposite end.

There are, of course, many alternative embodiments and modifications ofthe present invention which are intended to be included within thespirit and scope of the following claims.

What is claimed is:
 1. An inflation assembly timing member comprisingdiscrete openings in relation to preselected locations for introductionof inflation gas within a target airbag; wherein said timing membercomprises a fabric comprising warp yarns having a denier between 630 and2000 and fill yarns having a denier between 630 and 1400; wherein acoating has been applied to at least a portion of said fabric; andwherein said fabric exhibits (a) an average overall tensile strength ofat least 900 psi in the warp direction and an average overall tensilestrength of at least 700 psi in the fill direction, both up to atemperature of at least 80° C., (b) a permeability to air of at most 0.3cfm at 2,500 Pa, and (c) no appreciable blocking upon inflation uponstorage in an environment heated to about 100° C. for 7 days.
 2. Theinflation assembly of claim 1 wherein said fibers within said fabric areselected from the group consisting of polyester, polyarnide, polyaramid,and any combinations thereof.
 3. The inflation assembly of claim 2wherein said warp direction yarn is a multi-ply yarn having anelongation at break of at least 43%.
 4. The inflation assembly of claim3 wherein said fill direction yarn is at least a single-ply yarn havingan elongation at break of at most 35%.